Comment by mrob

>humanoid, tazer / machine gun carrying robots

Any AI smart enough to be a existential risk is surely capable of manufacturing swarms of insect-sized drones equipped with lethal poison injectors. This is enough to wipe out 99% of humanity within a few days. The 1% who were able to defend themselves become easy targets in the ensuing collapse of civilization. But I don't think this will actually happen: I only have human intelligence, so my ideas are stupid compared to what a super-intelligent AI could come up with. A truly smart plan won't allow for any survivors.